U.S. patent application number 09/843077 was filed with the patent office on 2002-10-31 for wafer stage carrier and removal assembly.
This patent application is currently assigned to Nikon Corporation. Invention is credited to Binnard, Michael, Watson, Douglas C..
Application Number | 20020159045 09/843077 |
Document ID | / |
Family ID | 25289030 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020159045 |
Kind Code |
A1 |
Binnard, Michael ; et
al. |
October 31, 2002 |
Wafer stage carrier and removal assembly
Abstract
A device and method are provided to remove a wafer stage carrier
carrying a wafer stage assembly from an exposure apparatus. The
wafer stage carrier may be removably fastened to the apparatus
frame of the exposure apparatus by any types of mechanical
fasteners. The removal assembly includes a set of expandable
supports and a set of removal supports. When the apparatus frame
supports the wafer stage carrier, the wafer stage carrier hangs
above a stationary surface, such as the ground. To remove the wafer
stage carrier, the set of expandable supports is expanded until it
reaches the ground and is capable of supporting the weight of the
wafer stage carrier. At this juncture, the mechanical fasteners may
be removed to allow the weight of the wafer stage carrier to
transfer from the apparatus frame to the expandable supports. The
set of expandable supports may reduce its expansion to lower the
wafer stage carrier away from the exposure apparatus until the set
of removal supports reaches the ground and supports the weight of
the wafer stage carrier.
Inventors: |
Binnard, Michael; (Belmont,
CA) ; Watson, Douglas C.; (Campbell, CA) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT &
DUNNER LLP
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Assignee: |
Nikon Corporation
|
Family ID: |
25289030 |
Appl. No.: |
09/843077 |
Filed: |
April 27, 2001 |
Current U.S.
Class: |
355/72 ;
310/12.06; 310/12.31; 318/625; 355/53; 355/75 |
Current CPC
Class: |
G03F 7/709 20130101;
G03F 7/70825 20130101; G03F 7/70716 20130101; Y10S 414/135
20130101 |
Class at
Publication: |
355/72 ; 355/75;
355/53; 310/12; 318/625 |
International
Class: |
G03B 027/58 |
Claims
We claim:
1. A removal device to facilitate removing devices constructed in a
sub-assembly from a main assembly, the sub-assembly being removably
attached to the main assembly, comprising: at least one expandable
support, when in an expanded state, supporting the sub-assembly on
a stationary surface; and at least one removal support to support
and remove the sub-assembly away from the main assembly after
detaching the sub-assembly from the main assembly.
2. The removal device of claim 1, wherein the at least one
expandable support is at least one expandable pneumatic
support.
3. The removal device of claim 2, wherein the at least one
expandable pneumatic support comprises at least one air spring.
4. The removal device of claim 3, further comprising: a vacuum
source to provide vacuum to lift the at least one air spring away
from the stationary surface.
5. The removal device of claim 1, wherein the at least one
expandable support is at least one retractable mechanical
support.
6. The removal device of claim 5, wherein the at least one
retractable mechanical support comprises at least one retractable
leg.
7. The removal device of claim 1, wherein the at least one
expandable support is at least one chargeable electromagnetic
support.
8. The removal device of claim 7, wherein the at least one
chargeable electromagnetic support comprises at least one
actuator.
9. The removal device of claim 1, wherein the at least one removal
support is one of a plurality of wheels, a plurality of casters, at
least one pneumatic bearing, and a combination thereof.
10. The removal device of claim 1, further comprising: at least one
roller guide to facilitate removing the sub-assembly away from the
main assembly.
11. The removal device of claim 10, wherein the at least one roller
guide comprises: a first portion of the at least one roller guide
provided on an outer periphery of the sub-assembly; and a second
portion of the at least one roller guide, corresponding to the
first portion, provided on an inner periphery of the main
assembly.
12. The removal device of claim 11, wherein the first portion of
the at least one roller guide comprises at least one rail, and the
second portion of the at least one roller guide comprises at least
one cam follower.
13. The removal device of claim 1, wherein the at least one
expandable support and the at least one removal support are
provided on an underside of a base plate of the sub-assembly.
14. The removal device of claim 13, wherein the at least one
expandable support and the at least one removal support are
positioned adjacent to sections on the underside of the base plate
where the sub-assembly attaches to the main assembly.
15. A projection lens assembly comprising the removal device of
claim 1.
16. A photolithography system comprising the removal device of
claim 1.
17. An object manufactured with the photolithography system of
claim 16.
18. A wafer on which an image has been formed by the
photolithography system of claim 16.
19. A method for removing a carrier for devices constructed in a
sub-assembly from a main assembly, comprising: expanding at least
one expandable support until the sub-assembly is supported thereby
on a stationary surface; detaching the sub-assembly from the main
assembly; and reducing expansion of the at least one expandable
support to remove the sub-assembly from the main assembly.
20. The method of claim 19, wherein the at least one expandable
support is at least one pneumatic support, and the expanding
comprises inflating the at least one pneumatic support.
21. The method of claim 20, wherein the at least one pneumatic
support is at least one air spring.
22. The method of claim 21, further comprising: creating a vacuum
in the at least one air spring to lift the at least one pneumatic
support clearing off the stationary surface.
23. The method of claim 19, wherein the at least one expandable
support is at least one retractable mechanical support, and the
expanding comprises extending at least one retractable leg.
24. The method of claim 19, wherein the at least one expandable
support is at least one chargeable electromagnetic support, and the
expanding comprises charging at least one electromagnetic actuator
to support the sub-assembly.
25. The method of claim 19, wherein the at least one expandable
support is expanded until the sub-assembly is kinematically
supported thereby.
26. The method of claim 19, wherein each of the at least one
expandable support is positioned adjacent to a section on the
underside of the sub-assembly where the sub-assembly attaches to
the main assembly.
27. The method of claim 19, further comprising providing at least
one track guide around a periphery of the sub-assembly to
facilitate removal of the sub-assembly from the main assembly.
28. A method for disassembling a projection lens assembly utilizing
the removal method of claim 19.
29. A method for disassembling a photolithography system utilizing
the removal method of claim 19.
30. A wafer stage carrier for carrying a wafer stage assembly, the
wafer stage carrier being removably connected to an apparatus frame
of an exposure apparatus, the wafer stage carrier comprising: a
wafer stage base plate having a plurality of body supports for
attaching the wafer stage carrier to the apparatus frame; at least
one expandable support, when in an expanded state, supporting the
wafer stage carrier on a stationary surface; and at least one
removal support to support and remove the wafer stage carrier away
from the exposure apparatus after detaching the wafer stage carrier
from the apparatus frame of the exposure apparatus.
31. The wafer stage carrier of claim 30, wherein the at least one
expandable supports is at least one expandable pneumatic
support.
32. The wafer stage carrier of claim 31, wherein the at least one
expandable pneumatic support comprises at least one air spring.
33. The wafer stage carrier of claim 32, further comprising: a
vacuum source to provide vacuum to and lift the at least one air
spring away from the stationary surface.
34. The wafer stage carrier of claim 31, wherein the at least one
expandable support is at least one retractable mechanical
support.
35. The wafer stage carrier of claim 34, wherein the at least one
retractable mechanical support comprises at least one retractable
leg.
36. The wafer stage carrier of claim 31, wherein the at least one
expandable support is at least one chargeable electromagnetic
support.
37. The wafer stage carrier of claim 36, wherein the at least one
chargeable electromagnetic support comprises at least one
actuator.
38. The wafer stage carrier of claim 30, wherein the at least one
removal support is one of a plurality of wheels, a plurality of
casters, at least one pneumatic bearing, and a combination
thereof.
39. The wafer stage carrier of claim 30, further comprising: at
least one roller guide to facilitate removing the sub-assembly away
from the main assembly.
40. The wafer stage carrier of claim 39, wherein the at least one
roller guide comprises: a first portion of the at least one roller
guide provided on an outer periphery of the sub-assembly; and
second portion of the at least one roller guide, corresponding to
the first portion, provided on an inner periphery of the main
assembly.
41. The wafer stage carrier of claim 40, wherein the first portion
of the at least one roller guide comprises at least one rail, and
the second portion of the at lest one roller guide comprises at
least one cam follower.
42. The wafer stage carrier of claim 30, wherein the at least one
expandable support and the at least one removal support are
provided on an underside of a base plate of the sub-assembly.
43. The wafer stage carrier of claim 42, wherein the at least one
expandable support and the at least one removal support are
positioned adjacent to the plurality of body supports on the
underside of the wafer stage base plate.
44. A projection lens assembly comprising the wafer stage carrier
of claim 30.
45. A photolithography system comprising the wafer stage carrier of
claim 30.
46. An object manufactured with the photolithography system of
claim 45.
47. A wafer on which an image has been formed by the
photolithography system of claim 45.
48. A method for removing a wafer stage carrier from an exposure
apparatus, the wafer stage carrier being removably connected to an
apparatus frame of the exposure apparatus, the method comprising:
expanding at least one expandable support until the wafer stage
carrier is supported thereby on a stationary surface; detaching the
wafer stage carrier from the apparatus frame; and reducing
expansion of the at least one expandable support to remove the
wafer stage carrier from the exposure apparatus.
49. The method of claim 48, wherein the at least one expandable
support is at least one pneumatic support, and the expanding
comprises inflating the at least one pneumatic support.
50. The method of claim 49, wherein the at least one pneumatic
support is at least of air spring.
51. The method of claim 50, further comprising: creating a vacuum
in the at least one air spring to lift the at least one pneumatic
support clearing off the stationary surface.
52. The method of claim 48, wherein the at least one expandable
support is expanded until the wafer stage carrier is kinematically
supported thereby.
53. The method of claim 48, wherein the at least one expandable
support is positioned adjacent to a section of the underside of the
wafer stage carrier where the wafer stage carrier attaches to the
apparatus frame.
54. The method of claim 48, further comprising providing at least
one track guide around a periphery of the wafer stage carrier to
facilitate removal of the wafer stage carrier from the exposure
apparatus.
55. A method for disassembling a projection lens assembly utilizing
the method of claim 48.
56. A method for disassembling a photolithography system utilizing
the method of claim 48.
57. A method for attaching a carrier for devices constructed in a
sub-assembly to a main assembly, comprising: expanding at least one
expandable support until the sub-assembly is supported thereby on a
stationary surface; attaching the sub-assembly to the main
assembly; and reducing expansion of the at least one expandable
support to support the sub-assembly by the main assembly.
58. A method for making an exposure apparatus utilizing the method
of claim 57.
59. A method of making a wafer utilizing the exposure apparatus
made by the method of claim 58.
60. A method of making a device including at least an exposure
process, wherein the exposure process utilizes the exposure
apparatus made by the method of claim 58.
61. A method for making an exposure apparatus, the method
comprising steps of: providing a main assembly including an
exposure device; and removably attaching a sub-assembly to a part
of the main assembly with a removal device, the removal device
comprising: at least one expandable support, when in an expanded
state, supporting the sub-assembly on a stationary surface; and at
least one removal support to support and remove the sub-assembly
away from the main assembly after detaching the sub-assembly from
the main assembly.
62. A method of making a wafer utilizing the exposure apparatus
made by the method of claim 61.
63. A method of making a device including at least an exposure
process, wherein the exposure process utilizes the exposure
apparatus made by the method of claim 61.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a carrier for sensitive devices
and method for removing the sensitive devices constructed in a
sub-assembly from a main assembly. In particular, this invention
relates to a carrier and a removal assembly, such as a wafer stage
carrier and removal assembly, to remove the wafer stage carried by
the wafer stage carrier from an exposure apparatus. The exposure
apparatus may be the type used in a photolithography process to
manufacture semiconductor substrates.
[0003] 2. Description of the Related Art
[0004] In manufacturing integrated circuits using a
photolithography process, light is transmitted through non-opaque
portions of a pattern on a reticle, or photomask, through a
projection exposure apparatus, and onto a wafer of specially-coated
silicon or other semiconductor material. The uncovered portions of
the coating, that are exposed to light, are cured. The uncured
portions of the coating are removed by an acid bath. Then, the
layer of uncovered silicon is altered to produce one layer of the
multi-layered integrated circuit. Conventional systems use visible
and ultraviolet light for this process. Recently, however, visible
and ultraviolet light have been replaced with electron, x-ray, and
laser beams, which permit smaller and more intricate patterns.
[0005] As the miniaturization of a circuit pattern progresses, the
focus depth of the projection exposure apparatus becomes very
small, making it difficult to align accurately the overlay of
circuit patterns of the multi-layered integrated circuit. As a
result, a primary consideration for an overall design of the
photolithography system includes building components of the system
that achieve precision by maintaining small tolerances. Any
vibration, distortion, or misalignment caused by internal, external
or environmental disturbances must be kept at minimum. When these
disturbances affect an individual part, the focusing properties of
the photolithography system are collectively altered.
[0006] Occasionally, a portion of the photolithography system,
i.e., a carrier of a sub-assembly, needs to be removed from the
main assembly for servicing purposes, periodic maintenance, or
other reasons. In one example, the sub-assembly may be a wafer
stage carried by a wafer stage carrier that needs to be removed
from the exposure apparatus as the main assembly. In an extremely
sensitive and delicate system, such as the photolithography system
where any types of disturbances, such as vibration, heat, and the
like, may alter the accurate alignment of the system, there is a
need for a wafer stage carrier and method to remove the wafer stage
carrier from the exposure apparatus without causing any
disturbances, or with minimized disturbances, to other parts and
components of the photolithography system.
SUMMARY OF THE INVENTION
[0007] The advantages and purposes of the invention will be set
forth in part in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The advantages and purposes of the invention will be
realized and attained by the elements and combinations particularly
pointed out in the appended claims.
[0008] To attain the advantages and consistent with the principles
of the invention, as embodied and broadly described herein, a first
aspect of the invention is a carrier for sensitive devices to
facilitate removing the sensitive devices constructed in a
sub-assembly from a main assembly. The sub-assembly is removably
attached to the main assembly. The carrier comprises a set of
expandable supports, when in an expanded state, supporting the
sub-assembly on a stationary surface, and a set of removal supports
to support and remove the sub-assembly away from the main assembly
after detaching the sub-assembly from the main assembly.
[0009] A second aspect of the present invention is a method for
removing a carrier for sensitive devices constructed in a
sub-assembly from a main assembly. The method comprises expanding a
set of expandable supports until the sub-assembly is supported
thereby on a stationary surface, and detaching the sub-assembly
from the main assembly. The method also comprises reducing
expansion of the set of expandable supports to remove the
sub-assembly from the main assembly.
[0010] A third aspect of the present invention is a wafer stage
carrier for carrying a wafer stage assembly. The wafer stage
carrier is removably connected to an apparatus frame of an exposure
apparatus. The wafer stage carrier comprises a wafer stage base
plate having a plurality of body supports for attaching the wafer
stage carrier to the apparatus frame, and a set of expandable
supports, which when in an expanded state, supports the wafer stage
carrier on a stationary surface. The wafer stage carrier also
comprises a set of removal supports to support and remove the wafer
stage carrier away from the exposure apparatus after detaching the
wafer stage carrier from the apparatus frame of the exposure
apparatus.
[0011] A fourth aspect of the present invention is a method for
removing a wafer stage carrier from an exposure apparatus. The
wafer stage carrier is removably connected to an apparatus frame of
the exposure apparatus. The method comprises expanding a set of
expandable supports until the wafer stage carrier is supported
thereby on a stationary surface, and detaching the wafer stage
carrier from the apparatus frame. The method also comprises
reducing expansion of the set of expandable supports to remove the
wafer stage carrier from the exposure apparatus.
[0012] A fifth aspect of the present invention is a method for
attaching a carrier for devices constructed in a sub-assembly to a
main assembly. The method comprises expanding at least one
expandable support until the sub-assembly is supported thereby on a
stationary surface, attaching the sub-assembly to the main
assembly, and reducing expansion of the at least one expandable
support to support the sub-assembly by the main assembly.
[0013] A sixth aspect of the present invention is a method for
making an exposure apparatus comprising steps of providing a main
assembly including an exposure device, and removably attaching a
sub-assembly to a part of the main assembly with a removal device.
The removal device comprises at least one expandable support, when
in an expanded state, supporting the sub-assembly on a stationary
surface, and at least one removal support to support and remove the
sub-assembly away from the main assembly after detaching the
sub-assembly from the main assembly.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are not restrictive of the invention as
claimed. Additional advantages will be set forth in the description
which follows, and in part will be understood from the description,
or may be learned by practice of the invention. The advantages and
purposes may be obtained by means of the combinations set forth in
the attached claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate several
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0016] FIG. 1 is a top perspective view from a front side of a
wafer stage carrier consistent with the principles of the present
invention;
[0017] FIG. 2 is a bottom perspective view from a rear side of the
wafer stage carrier shown in FIG. 1;
[0018] FIGS. 3A-3C are schematic elevation views illustrating the
wafer stage carrier and method consistent with the principles of
the present invention;
[0019] FIG. 3D is a schematic front view illustrating a set of
roller guides of the wafer stage carrier shown in FIGS. 3A-3C;
[0020] FIG. 4 is a schematic view of an exposure apparatus;
[0021] FIG. 5 is a flow chart outlining a process for manufacturing
semiconductor wafers; and
[0022] FIG. 6 is a flow chart outlining the semiconductor
manufacturing process in further detail.
DESCRIPTION OF THE INVENTION
[0023] Reference will now be made in detail to an embodiment of the
device, assembly and method consistent with the principles of the
present invention, examples of which are illustrated in the
accompanying drawings. The invention will be further clarified by
the following examples, which are intended to be exemplary of the
invention.
[0024] The device, assembly and method consistent with the
principles of the present invention are useful to allow removal of
a carrier for sensitive devices constructed in a sub-assembly from
a main assembly. One application of this invention is in a
photolithography system to manufacture semiconductor substrates,
whereby a wafer stage carrier of a wafer stage 66 (shown in FIG. 4)
constitutes the sub-assembly, and an exposure apparatus 21
constitutes the main assembly. The principles of this invention are
similarly applicable to other parts of the photolithography system,
or other sensitive system having high-accuracy in alignment. Thus,
this invention is not limited to any particular application.
Rather, the device, assembly and method disclosed herein could be
used in any system configured to embody a sub-assembly removably
attached to a main assembly.
[0025] One consideration in designing the wafer stage carrier and
method of the present invention is self-sufficiency of the device
which allows easy removal, moving, and installation of the wafer
stage carrier without requiring a forklift or other similar tools.
Another consideration is to minimize the empty space required
underneath the wafer stage carrier to maximize the stiffness of the
baseplate of the wafer stage carrier.
[0026] As illustrated in FIG. 1, the wafer stage carrier 200 may
carry components of wafer stage 66, including wafer stage base 66a
and mover assembly bases 66b and 66c. The components of wafer stage
66 are supported on a base plate 208 by a plurality of body
supports 202, 204, and 206. Body support 202 is provided on a rear
side 201 of wafer stage carrier 200, while body supports 204 and
206 are on a front side 203 thereof. Each of body supports 202,
204, and 206 has a top mounting surface 202a, 204a, and 206a,
respectively, for connecting wafer stage carrier 200 to exposure
apparatus 21, such as the apparatus frame 72 of exposure apparatus
21 shown in FIG. 4. Body support 202 may also have a bottom
mounting surface 202b (shown in FIG. 2) for connecting body support
202 to wafer stage carrier 200. Mechanical fasteners, for example,
bolts, screws, clamps, or equivalents, may be used to fasten wafer
stage carrier 200 to apparatus frame 72.
[0027] As illustrated in FIG. 2, the underside of base plate 208
may have a ribbed design to provide additional structural strength
to wafer stage carrier 200. Consistent with the principles of the
present invention, a wafer stage removal assembly is provided on
the underside of base plate 208. The removal assembly includes a
set of expandable support and a set of removal support. The set of
expandable support may be a set of pneumatic support, such as, a
plurality of air springs 212a, 212b, 214, and 216. In the
embodiment shown, air springs 212a and 212b are smaller in size
compared with air springs 214 and 216 to illustrate that a pair of
air springs may serve the same function as one with a higher
capacity.
[0028] Each of air springs 212a, 212b, 214, and 216 is basically an
expandable rubber balloon and generally commercially available
through a tire manufacturing company, such as Goodyear, Firestone,
etc. Each of air springs 212a, 212b, 214, and 216 usually comes
with a pair of metal plates sandwiching the air spring. In this
embodiment, one part of the metal plates (not shown) is for
attachment to the underside of wafer stage carrier 200, and the
other part 222a, 222b, 224, or 226 is for supporting each air
spring 212a, 212b, 214, or 216, respectively, on another stationary
surface, such as the ground.
[0029] Also consistent with the principles of the present
invention, the set of removable support includes a plurality of
rollers to slidably remove wafer stage carrier 200 from exposure
apparatus 21. In one embodiment, there are three rollers 242, 244,
and 246. Rollers 242, 244, and 246 may be casters, manually steered
wheels, ball casters, or fixed wheels. Alternatively, the rollers
may also be air bearings provided on the underside of base plate
208 to allow wafer stage carrier 200 to levitate above the
stationary surface as being removed from the main assembly.
[0030] In the embodiment shown in FIG. 2, the set of expandable
support and the set of removal support are positioned adjacent to
body supports 202, 204, and 206, i.e., around the sections where
wafer stage carrier 200 is attached to segments 71 of apparatus
frame 72 (shown in FIG. 4). According to this embodiment, when the
weight of wafer stage carrier 200 is transferred from body supports
202, 204, and 206 to expandable support, i.e., air springs 212a,
212b, 214, and 216, respectively, and to removal support, i.e.,
rollers 242, 244, and 246, base plate 208 as well as other
components of wafer stage carrier 200 experience minimum
deformation and distortion. This invention anticipates that the
expandable support and removal support may have different
positional configurations to meet other design specifications.
[0031] In alternative embodiments, the set of expandable support
may be a set of retractable mechanical support, or a set of
chargeable electromagnetic support, or any combination of the above
and equivalents thereof. For example, the set of retractable
mechanical support may be a plurality of robotic legs (not shown)
which may be extended from or retracted to base plate 208 as
necessary. Similarly, the set of chargeable electromagnetic support
may be a plurality of actuators (not shown), each generating
variable electromagnetic field to support wafer stage carrier 200
and lower it until reaching the stationary surface.
[0032] Further consistent with the principles of the present
invention, wafer stage carrier 200 may also be provided with a set
of roller guides 280 (shown in FIG. 3D) to facilitate removal of
wafer stage carrier 200 from the main body. In exposure apparatus
21, such as the one shown in FIG. 4, there is commonly a tight
clearance of approximately 5-10 mm between an outer periphery of
wafer stage 66 and apparatus frame 72. To protect sensitive
components of wafer stage carrier 200 and exposure apparatus 21,
roller guides 280 are provided to cushion the outer periphery of
wafer stage carrier 200 from accidental bumping with the inner
periphery of the main assembly. Roller guides 280 may include, for
example, a cam follower 282 attached to the inner periphery of
segments 71 of apparatus frame 72, and a corresponding rail 284
attached to the outer periphery of wafer stage carrier 200. Vice
versa, cam follower 282 may be attached to the outer periphery of
wafer stage carrier 200, while rail 284 attached to the inner
periphery of segments 71.
[0033] The removal assembly consistent with the principles of the
present invention operates as follows and as schematically
illustrated in FIGS. 3A-3D. For exemplary purposes, only one
expandable support, i.e., one air spring 212a, 212b, 214, or 216,
and one roller 242, 244, or 246 are shown.
[0034] In FIG. 3A, wafer stage carrier 200 is attached to segments
71 of apparatus frame 72 via body supports 202, 204, and 206. Wafer
stage carrier 200, as well as all components of the removal
assembly (only one expandable support, i.e., one air spring 212a,
212b, 214, or 216, and one roller 242, 244, or 246 are shown) hang
above stationary surface 82.
[0035] In FIG. 3B, when initiating the removal process, air springs
212a, 212b, 214, and 216 are inflated by feeding in air or other
fluid from one or more sources (not shown) so that air springs
212a, 212b, 214, and 216 extend downwards until metal plates 222a,
222b, 224, and 226, respectively, reach stationary surface 82. In
one preferred embodiment, air springs 212a, 212b, 214, and 216 are
inflated until the overall internal pressure exerts a support force
equivalent to the weight of wafer stage carrier 200.
[0036] At this juncture, wafer stage carrier 200 may be detached
from apparatus frame 72 by loosening and removing the fasteners
connecting body supports 202, 204, and 206 to segments 71. Body
support 202 on the rear side 201 may remain attached to the main
body by removing the fasteners on bottom mounting surface 202b so
that wafer stage carrier 200 is clear from other components of
exposure apparatus 21, such as lens assembly 78 of exposure
apparatus 21 as shown in FIG. 4. At this equilibrium, wafer stage
carrier 200 is kinematically supported by air springs 212a, 212b,
214, and 216. The term kinematic means that a component or an
assembly is supported with exactly the necessary amount of
constraint without over constraining. The weight of wafer stage
carrier 200 is thus swimmingly shifted from being supported by body
supports 202, 204, and 206, to the expandable support, i.e., air
springs 212a, 212b, 214, or 216.
[0037] In FIG. 3C, air springs are then deflated to lower detached
wafer stage carrier 200 from exposure apparatus 21 until the
removal support, i.e., rollers 242, 244, and 246, reach stationary
surface 82 and wafer stage carrier 200 rests thereon.
[0038] Thereafter, as illustrated in FIG. 3D, wafer stage carrier
200 may be removed from exposure apparatus 21, for example, by
pulling or pushing sub-assembly 200 toward front side 203.
Alternatively, in the case where exposure apparatus 21 does not
have any protruding components, wafer stage carrier 200 may be
removed by pulling or pushing wafer stage carrier 200 toward either
front side 203 or rear side 201. The set of roller guides 280
protect wafer stage carrier 200 from accidental bumping into
exposure apparatus 21 during such removal. During movement of the
wafer stage carrier 200, air springs 212a, 212b, 214, and 216 could
be inflated to lift the rollers 242, 244, and 246 off the
stationary surface to allow steering the wafer stage carrier 200.
The wafer stage carrier 200 could be allowed small horizontal
motion in the case of fixed the rollers, because the air springs
212a, 212b, 214, and 216 have low horizontal stiffness. For larger
motions, the wafer stage carrier 200 can be repeatedly raised on
air springs, pushed to side of the wafer stage carrier 200 turn it,
and lowered onto the rollers.
[0039] As can be seen, to attach wafer stage carrier 200 to the
main assembly, i.e. apparatus frame 72 of exposure apparatus 21, a
reversed process may be followed as shown in FIG. 3C by positioning
wafer stage carrier 200 under segment 71 of apparatus frame 72 so
that body supports 204 and 206 are approximately aligned with the
fasteners on segment 71. Then, as shown in FIG. 3B, air springs
212a, 212b, 214, and 216 may be inflated to raise wafer stage
carrier 200 until reaching the equilibrium such that top mounting
surface 204a and 206a are aligned with the fasteners on segment 71,
and bottom mounting surface 202b is aligned with the corresponding
fasteners on rear side 201 of base plate 208. Thereafter, at this
juncture, wafer stage carrier 200 is attached to exposure apparatus
21 by fastening the fasteners on body supports 202, 204, and 206.
Once wafer stage carrier 200 is securely fastened to exposure
apparatus 21, air springs 212a, 212b, 214, and 216 may be deflated
again, as shown in FIG. 3A.
[0040] FIG. 4 illustrates a wafer stage 66 as a part of exposure
apparatus 21 of a photolithography system to manufacture
semiconductor wafers 68. All of the elements of wafer stage carrier
200 are not shown. Wafer stage 66 positions the semiconductor wafer
68 as wafer stage 66 is being accelerated by a stage force (not
shown) generated in response to a wafer manufacturing control
system (not shown). The wafer manufacturing control system is the
central computerized control system executing the wafer
manufacturing process. To permit smaller and more intricate circuit
pattern, projection lens assembly 78 must accurately focus the
energy beam to align the overlay of circuit patterns of the
multi-layered integrated circuit.
[0041] An apparatus frame 72 supports projection lens assembly 78.
In operation, exposure apparatus 21 transfers a pattern of an
integrated circuit from reticle 80 onto semiconductor wafer 68.
Exposure apparatus 21 can be mounted to a base 82 (stationary
surface), i.e., the ground or via a vibration isolation system (not
shown). Apparatus frame 72 is rigid and supports the components of
exposure apparatus 21, including reticle stage 76, wafer stage 66,
lens assembly 78, and illumination system 74.
[0042] Illumination system 74 includes an illumination source 84 to
emit a beam of light energy. Illumination system 74 also includes
an illumination optical assembly 86 to guide the beam of light
energy from illumination source 84 to lens assembly 78. The beam
selectively illuminates different portions of reticle 80 and
exposes wafer 68.
[0043] Lens assembly 78 projects and/or focuses the light passing
through reticle 80 to wafer 68. Lens assembly 78 may magnify or
reduce the image illuminated on reticle 80. Lens assembly 78 may
also be a 1.times. magnification system.
[0044] Reticle stage 76 holds and positions reticle 80 relative to
lens assembly 78 and wafer 68. Similarly, wafer stage 66 holds and
positions wafer 68 with respect to the projected image of the
illuminated portions of reticle 80. Wafer stage 66 and reticle
stage 76 are moved by a plurality of motors 10.
[0045] There are several different types of photolithography
systems, including a scanning type and a step-and-repeat type. In
the scanning type photolithography system, illumination system 74
exposes the pattern from reticle 80 onto wafer 68 with reticle 80
and wafer 68 moving synchronously. Reticle stage 76 moves reticle
80 on a plane which is generally perpendicular to an optical axis
of lens assembly 78, while wafer stage 66 moves wafer 68 on another
plane generally perpendicular to the optical axis of lens assembly
78. Scanning of reticle 80 and wafer 68 occurs while reticle 80 and
wafer 68 are moving synchronously.
[0046] Alternately, in the step-and-repeat type photolithography
system, illumination system 74 exposes reticle 80 while reticle 80
and wafer 68 are stationary. Wafer 68 is in a constant position
relative to reticle 80 and lens assembly 78 during the exposure of
an individual field. Subsequently, between consecutive exposure
steps, wafer 68 is consecutively moved by wafer stage 66
perpendicular to the optical axis of lens assembly 78 so that the
next field of semiconductor wafer 68 is brought into position
relative to lens assembly 78 and reticle 80 for exposure. Following
this process, the images on reticle 80 are sequentially exposed
onto the fields of wafer 68.
[0047] The use of exposure apparatus 21 provided herein is not
limited to a photolithography system for a semiconductor
manufacturing. Exposure apparatus 21, for example, can be used as
an LCD photolithography system that exposes a liquid crystal
display device pattern onto a rectangular glass plate or a
photolithography system for manufacturing a thin film magnetic
head. Further, the present invention can also be applied to a
proximity photolithography system that exposes a mask pattern by
closely locating a mask and a substrate without the use of a lens
assembly. Additionally, the present invention provided herein can
be used in other devices, including other semiconductor processing
equipment, machine tools, metal cutting machines, and inspection
machines.
[0048] The illumination source 84 can be g-line (436 nm), i-line
(365 nm), KrF excimer laser (248 nm), ArF excimer laser (193 nm)
and F.sub.2 laser (157 nm). Alternatively, illumination source 84
can also use charged particle beams such as x-ray and electron
beam. For instance, in the case where an electron beam is used,
thermionic emission type lanthanum hexaboride (LaB.sub.6) or
tantalum (Ta) can be used as an electron gun. Furthermore, in the
case where an electron beam is used, the structure could be such
that either a mask is used or a pattern can be directly formed on a
substrate without the use of a mask.
[0049] With respect to lens assembly 78, when far ultra-violet rays
such as the excimer laser is used, glass materials such as quartz
and fluorite that transmit far ultra-violet rays is preferably
used. When the F.sub.2 type laser or x-ray is used, lens assembly
78 should preferably be either catadioptric or refractive (a
reticle should also preferably be a reflective type), and when an
electron beam is used, electron optics should preferably comprise
electron lenses and deflectors. The optical path for the electron
beams should be in a vacuum.
[0050] Also, with an exposure device that employs vacuum
ultra-violet radiation (VUV) of wavelength 200 nm or lower, use of
the catadioptric type optical system can be considered. Examples of
the catadioptric type of optical system include the disclosure
Japan Patent Application Disclosure No. 8-171054 published in the
Official Gazette for Laid-Open Patent Applications and its
counterpart U.S. Pat. No, 5,668,672, as well as Japan Patent
Application Disclosure No. 10-20195 and its counterpart U.S. Pat.
No. 5,835,275. In these cases, the reflecting optical device can be
a catadioptric optical system incorporating a beam splitter and
concave mirror. Japan Patent Application Disclosure No. 8-334695
published in the Official Gazette for Laid-Open Patent Applications
and its counterpart U.S. Pat. No. 5,689,377 as wall as Japan Patent
Application Disclosure No. 10-3039 and its counterpart U.S. patent
application Ser. No. 873,606 (Application Date: Jun. 12, 1997) also
use a reflecting-refracting type of optical system incorporating a
concave mirror, etc., but without a beam splitter, and can also be
employed with this invention. The disclosures in the abovementioned
U.S. patents, as well as the Japan patent applications published in
the Official Gazette for Laid-Open Patent Applications are
incorporated herein by reference.
[0051] Further, in photolithography systems, when linear motors
(see U.S. Pat. Nos. 5,623,853 or 5,528,118) are used in a wafer
stage or a reticle stage, the linear motors can be either an air
levitation type employing air bearings or a magnetic levitation
type using Lorentz force or reactance force. Additionally, the
stage could move along a guide, or it could be a guideless type
stage which uses no guide. The disclosures in U.S. Pat. Nos.
5,623,853 and 5,528,118 are incorporated herein by reference.
[0052] Alternatively, one of the stages could be driven by a planar
motor, which drives the stage by electromagnetic force generated by
a magnet unit having two-dimensionally arranged magnets and an
armature coil unit having two-dimensionally arranged coils in
facing positions. With this type of driving system, either one of
the magnet unit or the armature coil unit is connected to the stage
and the other unit is mounted on the moving plane side of the
stage.
[0053] Movement of the stages as described above generates reaction
forces which can affect performance of the photolithography system.
Reaction forces generated by the wafer (substrate) stage motion can
be released mechanically to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,528,118 and published
Japanese Patent Application Disclosure No. 8-166475. Additionally,
reaction forces generated by the reticle (mask) stage motion can be
mechanically released to the floor (ground) by use of a frame
member as described in U.S. Pat. No. 5,874,820 and published
Japanese Patent Application Disclosure No. 8-330224. The
disclosures in U.S. Pat. Nos. 5,528,118 and 5,874,820 and Japanese
Patent Application Disclosure No. 8-330224 are incorporated herein
by reference.
[0054] As described above, a photolithography system according to
the above described embodiments can be built by assembling various
subsystems, including each element listed in the appended claims,
in such a manner that prescribed mechanical accuracy, electrical
accuracy and optical accuracy are maintained. In order to maintain
the various accuracies, prior to and following assembly, every
optical system is adjusted to achieve its optical accuracy.
Similarly, every mechanical system and every electrical system are
adjusted to achieve their respective mechanical and electrical
accuracies. The process of assembling each subsystem into a
photolithography system includes mechanical interfaces, electrical
circuit wiring connections and air pressure plumbing connections
between each subsystem. Needless to say, there is also a process
where each subsystem is assembled prior to assembling a
photolithography system from the various subsystems. Once a
photolithography system is assembled using the various subsystems,
total adjustment is performed to make sure that every accuracy is
maintained in the complete photolithography system. Additionally,
it is desirable to manufacture an exposure system in a clean room
where the temperature and purity are controlled.
[0055] Further, semiconductor devices can be fabricated using the
above described systems, by the process shown generally in FIG. 5.
In step 301 the device's function and performance characteristics
are designed. Next, in step 302, a mask (reticle) having a pattern
is designed according to the previous designing step, and in a
parallel step 303, a wafer is made from a silicon material. The
mask pattern designed in step 302 is exposed onto the wafer from
step 303 in step 304 by a photolithography system described
hereinabove consistent with the principles of the present
invention. In step 305 the semiconductor device is assembled
(including the dicing process, bonding process and packaging
process), then finally the device is inspected in step 306.
[0056] FIG. 6 illustrates a detailed flowchart example of the
above-mentioned step 304 in the case of fabricating semiconductor
devices. In step 311 (oxidation step), the wafer surface is
oxidized. In step 312 (CVD step), an insulation film is formed on
the wafer surface. In step 313 (electrode formation step),
electrodes are formed on the wafer by vapor deposition. In step 314
(ion implantation step), ions are implanted In the wafer. The above
mentioned steps 311-314 form the preprocessing steps for wafers
during wafer processing, and selection is made at each step
according to processing requirements.
[0057] At each stage of wafer processing, when the above-mentioned
preprocessing steps have been completed, the following
post-processing steps are implemented. During post-processing,
initially, in step 315 (photoresist formation step), photoresist is
applied to a wafer. Next, in step 316, (exposure step), the
above-mentioned exposure device is used to transfer the circuit
pattern of a mask (reticle) to a wafer. Then, in step 317
(developing step), the exposed wafer is developed, and in step 318
(etching step), parts other than residual photoresist (exposed
material surface) are removed by etching. In step 319 (photoresist
removal step), unnecessary photoresist remaining after etching is
removed.
[0058] Multiple circuit patterns are formed by repetition of these
preprocessing and post-processing steps.
[0059] It will be apparent to those skilled in the art that various
modifications and variations can be made in the sub-assembly, the
expandable support, the removal support, and the methods described,
the material chosen for the present invention, and in construction
of the sub-assembly, the main assembly, the photolithography
systems as well as other aspects of the invention without departing
from the scope or spirit of the invention.
[0060] Other embodiments of the invention will be apparent to those
skilled in the art from consideration of the specification and
practice of the invention disclosed herein. It is intended that the
specification and examples be considered as exemplary only, with a
true scope and spirit of the invention being indicated by the
following claims and their equivalents.
* * * * *